Screen Top PAR Reduction

[ingchr1]

I did a test today to see what the difference in PAR was for my tank from screen top on to screen top off. I used a Seneye and the results are shown in the screenshots. The Seneye was kept in the same position on the sand about center tank. For the screen top on I passed the Seneye cord through the feed door.

PAR Reduction: 20%
PUR Reduction: 2-3%
Screen Top: Black Mesh 1/4"
Light: GHL Mitras LX7, 10" off water and 9" off screen top
Tank: 24" (L) 18" (W) 18" (D)

I changed the screen mesh from clear to black last night. Wish I had taken measurements with the clear as a comparison.

The black makes the overall appearance of the tank look better, a lot less glare on top and I also think the clear was contributing to excess light scatter in the tank.

Screen Top Off

Screen Top On

 

[ingchr1]

Here's the light settings.

 

[jda]

I tested before and found less than 2% difference with the 1/2 mesh. This was with Apogee 510. I wonder if a cosine corrected vs a non cosine corrected sensor played a part.

 

[ingchr1]

I tested before and found less than 2% difference with the 1/2 mesh. This was with Apogee 510. I wonder if a cosine corrected vs a non cosine corrected sensor played a part.

Would be interesting to know if results would be different with a different meter.

I have 1/4" mesh.

Was your mesh clear or black?

Wish I would have taken the same readings with the clear mesh, to see how the reduction compares to the black.

 

[ingchr1]

Also wonder if light reduction also depends upon light source (LED, MH or T5) as well?

 

[JoshO]

BRS did this a while back and got about 5% par reduction as the result

 

[andrewey]

Interesting- I tested mine years ago with the clear 1/4" mesh and found somewhere around a 3% reduction

 

[ingchr1]

How much of a role does the frame play? It does cover ~20% of the total surface area.

This measurement was in the center bottom. But is the frame blocking some light that was getting reflected back in off of the glass?

Or is it something with the Seneye itself and how it performs measurements as mentioned by @jda?

 

[ingchr1]

I have another tank and I'm seeing similar high results with the black mesh, ~14% reduction. But this tank has clear mesh that I was able to perform a comparison with. The clear mesh I'm seeing what others are reporting, 2-5% reduction.

For the black mesh I simply held it across the top. Again the Seneye was on the sand bed close to center.

PAR Reduction 1/4" Clear Mesh: ~2%
PAR Reduction 1/4" Black Mesh: ~14%
Light: Fluval Sea Marine & Reef Nano, 3" off of top, all channels at 100%
Tank: 16" (L) 12" (W) 15" (D)

Screen Top Off

Screen Top On (Clear Mesh)

Black Mesh Held Across Top

 

[ingchr1]

@Dana Riddle any thoughts on what I'm seeing with the black mesh?

 

[ingchr1]

I changed the black mesh from 1/4" to 3/4". With the 3/4" mesh I'm now seeing a ~10% reduction in PAR from no top. The 1/4" mesh I was seeing double that (20%). With the 3/4" mesh I'm also not seeing a PUR reduction, which I saw with the 1/4" mesh (2-3%).

Another major change is that I changed from the GHL Mitras to a T5 ATI SunPower with Reef Brite XHO Actinic Blue.

I took readings at a 9" mounting height and obtained the following:

PAR with Reef Brite at 60%: 1/4" = 120-125, 3/4" = 140
PAR with Reef Brite at 70%: 1/4" = 135, 3/4" = 150
PAR with Reef Brite at 80%: 1/4" = 140-145, 3/4" = 158
PAR with Reef Brite at 90%: 1/4" = 150, 3/4" = 165
PAR with Reef Brite at 100%: 1/4" = 150-155, 3/4" = 165

With the Reef Brite at 60% the PAR reduction was 11-14%.
With the Reef Brite at 100% the PAR Reduction was 6-9%.

A couple of observations with the readings.

• I was able to get a more stable PAR reading with the 3/4" mesh.
• The Reef Brite PAR did not really change from 90% to 100%. I'm controlling it with the Reef Brite Apex Dual Channel interface through my P4.

The readings were taken on the sand bed close to center.

The 3/4" mesh is bird netting that I already had from a hardware store.

I would really like to see a more controlled test with clear vs black, different mesh sizes, various power settings and different meters.

The following screen shots are with:

Screen Top: Black Mesh 3/4"
Light: 24" ATI SunPower 4-Bulb (2x Blue Plus, Actinic, Coral Plus) with Reef Brite XHO Actinic Blue, ATI Fixture 12" off water and 11" off screen top
Tank: 24" (L) 18" (W) 18" (D)

At this height the Reef Brite at 100% is giving me ~50PAR.

Reef Brite at 70% Top On

Reef Brite at 70% Top Off

Reef Brite at 0% Top On

Reef Brite at 100% Top On

 

[Mastiffsrule]

Evening

Thanks for taking time and writing this up. This is almost exactly where I am heading with my set up.

I have a 60 ATI hybrid that I modified to hold a 3rd T5 in the middle because I did not like the way the led‘s looked with the T5. So I have 2 coral +, 2 blue +, and I went with 2 Giesemann actinic. I am stuck on the led I want. My fixture is hanging from the ceiling so I am getting worried about weight. I was looking at the lumi lite from reefer breeder but may not be enough power.

How deep is you tank? I have a 180, so I am trying to estimate par based on your tank.

Thanks.

 

[ingchr1]

How deep is you tank?

My tank is 18" deep. I have sand, so the readings were at ~16".

 

[Dana Riddle]

@Dana Riddle any thoughts on what I'm seeing with the black mesh?

Hi Chris, Sometimes messages fall through the cracks, hence the tardy reply (and thanks for the reminder.) Your numbers seem reasonable - another data point. Thanks!

 

[ShepherdReefer]

Good stuff.